The investigators will recruit 237 patients with abdominal aortic aneurysms from the clinical surveillance programme at the Royal Infirmary, Edinburgh. Inclusion criteria will be patients with an abdominal aortic aneurysm >40 mm on ultrasound scanning. Exclusion criteria will include patients with anticipated or planned abdominal aortic aneurysm repair, women of child-bearing potential without contraception, inability to undergo magnetic resonance or computed tomography scanning, life expectancy of <2 years, and those with any form of collagen-vascular disease.